• Sodium nitrate was modified by solution combustion which is simple to operate and low cost. • The unusual structures like linear, needle and spherule grown at the surface and the interior of the modified salt. • The specific heat capacity of modified salt was enhanced a lot and has excellent thermal stability. • The enhancement of the specific heat capacity resulted from the unusual microscopic structures of NaNO 3 . Nitrate is extensively accepted as a kind of thermal storage material in solar thermal power generation because of its wide temperature range, high boiling point, low vapor pressure at high temperature, large specific heat and low viscosity. In this paper, the base salt NaNO 3 was modified by solution combustion method by using urea as fuel. The configuration and thermal properties of the as-prepared salt were investigated by using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Field Emission Scanning Electron Microscope (FE-SEM), X-ray Photoelectron Spectroscopy (XPS) and Differential Scanning Calorimeter (DSC). The outcome showed that the structure and thermal properties of NaNO 3 were improved by solution combustion process. The particle size and shape of as-prepared salt were modified. As the proportion of the fuel increasing, the special morphology like linear, needle and spherule gradually grown at the surface and the interior of the modified salt. The phase of as-prepared salt was remaining NaNO 3 . With the change of urea fuel, the specific heat was increased by 53.1% in solid phase, in addition increased by 51.2% in liquid phase in the maximum extent. This work not only studied the specific heat of chemically modified NaNO 3 , but also discussed the influence of NaNO 3 microscopic appearance on its properties, which provides a creative idea for molten salt modification and thermal energy storage.